Investigational testing of more than 4.32 million blood donations in the United States found nine that were confirmed to have Zika virus — a rate of around one contaminated sample per 480,654 donations, researchers reported today in The New England Journal of Medicine.
Paula Saá, PhD, senior director for operational research at the American Red Cross, and colleagues did not say if any infections resulted from the contaminated samples but reported that three of eight samples from donors with mosquito-borne infections could potentially have been infectious. A ninth donor with a Zika-positive sample had received an experimental Zika vaccine, they said.
Amid an ongoing epidemic centered in Brazil, the FDA first recommended in February 2016 that people in the U.S. who recently traveled to areas with active Zika transmission or who had a confirmed Zika infection not donate blood. The agency said 6 months later that all U.S. blood donations should be tested for the virus, which can cause a suite of serious birth defects in babies born to infected mothers, including microcephaly.
The testing has been costly and has yielded few positive samples, according to the current study, leading some experts to wonder if it should be stopped or revamped. The FDA met in December to consider whether to continue testing the blood supply for Zika but has not announced any changes.
Over 4 million U.S. blood donations were screened for Zika virus.
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FDA spokeswoman Tara G. Rabin said the agency does not usually comment on specific studies but evaluates them when making its decisions. Rabin told Infectious Disease News that the current FDA recommendations would remain in place “until such time as the FDA issues an update to its revised guidance.”
During the 15-month study period — which began on June 20, 2016, the day the Red Cross began screening for the virus — Saá and colleagues said testing the U.S. blood supply for Zika cost at least $42 million, or about $5.3 million per positive donation from a mosquito-infected donor. The screening was conducted using the Procleix Zika Virus Assay (Grifols Diagnostic Solutions) under an FDA-approved investigational new drug protocol. According to Saá and colleagues, testing for Zika beyond the investigational new drug assessment period is expected to cost $137 million annually.
Evan M. Bloch, MD, assistant professor of pathology at the Johns Hopkins University School of Medicine, and colleagues said increased screening costs are being passed down to blood centers, hospitals and patients.
“The current U.S. strategy for [Zika virus] screening comes at a cost with an unclear gain,” they wrote in a commentary that was also published today in The New England Journal of Medicine. “Although concerns about blood safety are vital, is it appropriate and possible to reverse blood-donation screening for [Zika virus] in the United States in light of emerging data?”
According to Bloch and colleagues, four people have ever acquired Zika through a transfusion — all in Brazil. Three of the patients received platelets, and one received packed red blood cells. Of the three living patients, none displayed clinical signs of Zika infection.
But Bloch and colleagues said it would be unprecedented in the U.S. to terminate a blood-screening program for a particular pathogen. Instead, they suggested possible alternatives, like compiling a limited inventory of Zika-screened blood donations that can be available for high-risk recipients, such as women receiving intrauterine transfusions.
According to Saá and colleagues, only one more positive donation was confirmed through Feb. 3, from a traveler who had returned from Mexico 4 days earlier.
Bloch and colleagues said the risk for Zika transmission through blood transfusions in the U.S. “remains low and is likely to diminish further as the pandemic continues to wane.”
“There is no doubt that [Zika virus] poses a major public health threat. However, the actual and perceived risks to the blood supply seem to be conflated,” they wrote. “The initial decision to test for [Zika virus] should not be condemned; a similar proactive response to HIV could have resulted in a reality very different from the pandemic that unfolded in the 1980s.” – by Gerard Gallagher
Bloch EM, et al. N Engl J Med. 2018;doi:10.1056/NEJMsb1704752.
Saá P, et al. N Engl J Med. 2018;doi:10.1056/NEJMoa1714977.
Disclosures: Bloch reports grants from Terumo BCT outside the submitted work. Saá reports other support from Grifols during the conduct of the study. Please see the articles for all other authors’ relevant financial disclosures.